Understanding Wireless

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Contents 1 Understanding Wireless 2 General Wireless Info 3 Some Review 4 Answers

[edit section] Understanding Wireless

The Network+ exam is becoming increasingly focused on wireless technology, so it is in your best interest to learn all of the current wireless standards and implementations. As with almost everything you must learn for the Network+ exam, it is crucial that you learn the differences between the standards/implementations and not just their features. Exam questions typically deal with “which one to implement”, not “what this implementation does”. Read and study accordingly.

IrDA (Infrared Data)

IrDA technology allows for communication over network through infrared beams. Infrared (a specturm of light) does not pass through solid objects, so a direct and clear path is essential for correct IrDA operation. IrDA typically operates at speeds around 16-25Mbps, but is known to operate at faster speeds with specialized equipment. It is a rather uncommon wireless networking technology given its inability to transmit signals where light is blocked. To do this, a lower frequency radio signal is necessary.

Bluetooth

Bluetooth (802.15.1) technology has received a lot of buzz lately, but it is basically a short-range wireless technology designed to allow for connectivity between portable consumer wireless devices and Bluetooth enabled wireless access points. Because of the relatively weak and low-frequency radio signal employed, Bluetooth is typically limited to a 20-35ft. access range. It is therefore usually limited to applications involving those portable consumer devices and not LAN technology, the most common application of Wi-Fi.

Wireless Fidelity (Wi-Fi)

Wi-Fi technology has really taken off in the last few years; it is probably almost as commonly known by its IEEE name, 802.11(letter). It is a technology that utilizes low-frequency (2.4 and 5GHz.), mid-powered radio waves to transmit data across wireless networks. There exist many “flavors” of the 802.11 standard; they differ primarily in speed and typical usage. These flavors are listed in a convenient table below:

Name-Standard	Speed (Mbps)	Usage
802.11a	54	5GHz band; outdated; used for LAN networking in businesses; expensive
802.11b	11	Cheaper 2.4GHz mode;
802.11g	54/108	Cross between A and B flavors; 2.4GHz at fast speeds. Also offers backwards compatibility
802.11n	300+	Next-generation, designed for very fast, high-end operation (probably not tested on Net+, but you never know!)

[edit section] General Wireless Info

One of the major factors or considerations that many companies think about before employing wireless technology is its somewhat high cost, though it is falling as time goes by. Still, cost is a major consideration. Wireless networks are also subject to interference from microwaves, phones, and other radio devices. Wireless networks are compatible with Ethernet using a MAC bridge that translates wireless frames into Ethernet frames.

Most wireless networks today connect using a sort of wireless “Star” topology – that is, in many setups, wireless devices all connect to a single wireless access point. Wireless traffic can be (but is not necessarily) switched, so information is not easily “sniffed” from a wireless network. However, Wi-Fi LAN’s have become somewhat notorious for their relative insecurities in terms of ease of access. Wi-Fi LAN’s are by default accessible without any sort of authentication and therefore vulnerable to different types of attacks and of course, mooching (wardriving). In addition, the built-in wireless encryption (WEP) is considered weak by today’s standards and has been replaced by WPA (Wi-Fi Protected Access), the most common wireless access control system available today.

Wireless networks can also operate in “ad-hoc” mode, meaning that nodes can, if they so incline, connect to each other individually in a sort of “mesh” scheme. This adds redundancy but makes management of such a network almost impossible.

[edit section] Some Review

1. Which of the following IEEE standards specifies Wi-Fi networking?

a. 802.3

b. 802.5c

c. 802.5d

d. 802.11

e. 802.21

2. You have a large (500+ user) network and wish to link some nodes (laptops) to the network wirelessly, while leaving most connected to existing hardware. Which of the following would be the most appropriate setup?

a. Connect the hubs and laptops in a wireless ring topology

b. Connect the laptops to the mainframe using 802.3 10BaseT

c. Employ ad-hoc mode between laptops

d. Employ a star topology, connecting the laptops to a WAP

e. Connect the laptops using IrDA

3. Which of the following is not a valid concern associated with Wi-Fi?

a. “War driving”

b. Limited signal range

c. Compatibility issues with Ethernet standard

d. Cost of Wi-Fi equipment

e. Interference

[edit section] Answers

1. 802.11 defines Wi-Fi networking, so the answer is D.

2. The best choice is D, because it allows your network to retain the existing physical topology while allowing the new nodes (laptops) to connect wirelessly in a manageable and scalable way.

3. All of the mentioned are concerns with the exception of C, which is absurd because Wi-Fi was specifically designed to work with 802.3 using a bridge.